In this section we prove Theorem REF .
We prove the APX-hardness of the two problems
Max-Adj\((\mbox{\footnotesize \textsl {linear}},\mbox{\footnotesize \textsl {interval}})\)  and Min-Brk\((\mbox{\footnotesize \textsl {linear}},\mbox{\footnotesize \textsl {interval}})\)  by two L-reductions (based on the same construction)
from the APX-hard problem
Max-IS-3, i.e.,
Maximum Independent Set in graphs of maximum degree 3 [1]}, [2]}.
